Question

Solve the equation 3x-y=5 and 3x+3y=21 by elimination by substitution method

Answer 1

Answer:

x = 3 , y = 4

Step-by-step explanation:

Elimination Method :

3x - y = 5  .......(1)

3x + 3y = 21  .......(2)

Now we'll subtract (2) from (1),

(1) - (2) =

-4y = -16

∴ y = 4

Now Substituting the value of y in (1) ;

∴ x = 3

Substitution Method :

3x - y = 5  .......(1)

3x + 3y = 21  .......(2)

Now, Taking (1),

y = 3x - 5  .......(3)

Now Substitute the Value of y from (3) in (2) ;

3x + 3 [ 3x - 5 ] = 21

3x + 9x - 15 = 21

12x - 15 = 21

12x = 36

∴ x = 3

Now Substituting the value of x in (1) ;

∴ y = 4